What Is Pitch?

A Few Pitches

Here are a few different pitches. Each of these are at a different height.

The three pitches in the soundfile above might be described respectively as:

Low

Medium

High

Beyond Traditional Ideas of Pitch

In traditional musical notation, pitch is indicated along the vertical axis of the stave. The pitches of sounds can be quickly described as being low, medium or high. However, we can split this into as many registers as are required (e.g. Low-Medium, High-Medium, etc.).

Multiple Pitches

This single horn sound contains multiple pitches playing at the same time.

Or one after the other:

Birdsong

This bridsong is a short melody of different notes following on from one another. Since the notes happen in quick succession, we hear this as a single gesture.

Fact

When we examine individual sounds in detail, we can discover that sounds are often made up of individual pitch elements. For more information, see: Complex Soundwaves.

This is a spectrogram of a triangle wave. A single triangle wave is itself made up of many individual pitches, we see them here as stripes.

What Causes Pitch?

Pitched sounds are caused by regular vibrations. If an object vibrates in a regular way (moving back and forth smoothly), then it will create a pitched sound. The less regular the sound vibrates, then the noisier it is.

We can experience this by rubbing our finger around the damp rim of a glass to make it sing.

Activity

Singing Glass

Instructions:

Ask someone at home if you can borrow a wine glass (or any glass with a stem).

Pick a glass that makes a good ring when you tap it.

Wet your finger and the rim of the glass.

Then, while holding the glass firmly with your non-writing hand, take the first finger of your writing hand and rub it smoothly and steadily around the rim of the glass.

Predicted Results:

If you are able to make smooth and steady regular motions around the rim, the glass should begin to sing, creating a pitched note.

If you move your writing hand in an irregular way around the glass, then no pitch will be created.

Why Is a Pitch Created?

The smooth and steady motion of the hand around the rim of the glass causes the glass to vibrate in a regular way, and thus produces a pitched sound.

Extra

By changing the level of liquid in the glass, it is possible to change the pitch. This is because the liquid dampens the vibrations where it touches the glass, thus changing the amount of the glass which is free to vibrate.

The more liquid in the glass, the smaller the surface that can vibrate and the higher the pitch produced.

This process is similar to the way in which changing the length of a string on a guitar or violin will change the pitch made (shorter string = higher pitch).

Changing the Pitch

Using technology, it is possible for us to change the pitch of sounds.

The process is known as pitch-shifting or transposition. This technique is often used in pop music or cartoons to create high pitched voices.